1. Field of the Invention
The present invention relates to an endoscope apparatus.
2. Description of the Related Art
Conventionally, in a medical field, endoscopes have been widely used, which are capable of observing organs inside body cavities and the like by elongated insertion portions being inserted into the body cavities, and performing various therapeutic treatments with use of treatment instruments that are inserted through insides of treatment instrument channels in accordance with necessity. Further, in an industrial field. endoscopes for industrial use are also widely used in observation and inspection of flaws, corrosion and the like in insides of boilers, turbines, engines. chemical plants and the like.
For the endoscopes for industrial use as above, endoscope apparatuses exist that are configured so that endoscopes having elongated insertion portions are attachable and detachable thereto and therefrom, and allow users to replace the endoscopes in response to inspection targets, as disclosed in Japanese Patent Application Laid-Open Publication No. 2001-224555.
In the endoscope apparatuses for industrial use as above. endoscopes having insertion portions of various lengths adapted to various inspection targets are lined up. The lengths of the insertion portions of the endoscopes correspond to a wide variety of lengths of 1 m to 30 m, and the main body sides have to be designed so that signal processing can be performed without a problem even if the endoscopes are attached thereto and detached therefrom.
Signal transmission includes transmission from the main body side to the distal end of the insertion portion, and transmission from the distal end of the insertion portion to the main body side, and therefore, a signal delay corresponding to the length which is twice as long as the insertion portion occurs. Namely since a normal electrical signal has a delay of approximately 5 nsec/m, the endoscope having the insertion portion of 1 m has a delay of 5 nsec×2=10 nsec, and the endoscope having the insertion portion of 30 m has a delay of 5 nsec×60=300 nsec.